Evaluating the welfare of different poultry stunning methods used before slaughter, including water bath, controlled atmosphere, and mechanical stunning systems.
Poultry slaughter welfare has one of the highest welfare impact potentials in animal agriculture due to the sheer number of birds affected. The shift from water bath to controlled atmosphere stunning represents one of the most significant welfare improvements available in the poultry industry — eliminating the hanging and shackling of fully conscious birds is a meaningful reduction in pre-slaughter suffering at enormous scale. Within CAS systems, the choice of gases matters: nitrogen or argon inert atmosphere systems achieve insensibility with minimal distress, while high-concentration CO2 causes visible gasping and distress before unconsciousness. The welfare hierarchy is clear: best practice is low-concentration CO2 multi-phase or inert gas CAS systems; standard practice in much of the world involves water bath stunning with significant pre-stun suffering; worst practice is uncontrolled conventional killing methods.